DHS 17 Electromagnetic Induction (Lecture Slides)

DHS Y6 Physics H2 [Electromagnetic Induction] 18/3/2025 [For Internal Use Only] lim.boonsiong@dhs.edu.sg 1 1 H2 Physics Topic 17: Electromagnetic Induction Key Differences Between Electromagnetism and Electromagnetic Induction 2 Important RulesFocusTopic • Right-hand grip rule (to find direction of B field around a current-carrying wire, produced by a current flowing through a circular loop of wire, and in solenoids • Fleming’s Left-hand Rule (to find the direction of magnetic force on a current-carrying conductor or moving charges in a magnetic field) How currents produce magnetic fields, and how these fields exert magnetic force on moving charges or current-carrying conductors Electromagnetism • Fleming’s Right-hand Rule (to find the direction of induced current) How a changing magnetic field induces an e.m.f. (and a current if the circuit is closed) Electromagnetic Induction 3 Fingers represent … with relevant diagramsRule - Curled fingers = current direction - Thumb = B field direction - Thumb = current direction - Curled fingers = B field direction Right-hand grip rule - First finger = B Field (N to S) - seCond finger = Current direction - ThuMb = Motion (Force) Fleming’s Left-hand Rule - First finger = B Field (N to S) - ThuMb = Motion (movement of conductor) - seCond finger = Induced Current direction Fleming’s Right-hand Rule Quick Reference for the Rules Electromagnetism Electromagnetic Induction 1. Introduction 2. Magnetic Flux and Magnetic Flux Linkage 3. Laws of Electromagnetic Induction • Faraday’s law • Lenz’s law 4. Applications 2 Contents 4 1 2 3 4

DHS Y6 Physics H2 [Electromagnetic Induction] 18/3/2025 [For Internal Use Only] lim.boonsiong@dhs.edu.sg 2 Guiding Question 1 electric current 5 magnetic field produces electric current ??magnetic field produces From Electromagnetism, we learnt that: What about?: What is required for this? Guiding Question 2 6 Can we achieve perpetual motion by invoking the magic of electromagnetism? Electromagnetism is a fundamental force where electric currents generate magnetic fields, influencing current carrying conductors and moving charges, and enabling motors. A changing magnetic field induces a current, which in turn produces another magnetic field, potentially continuing the cycle. Can we use principles of electromagnetism & EMI to create a machine forever without external energy? Cause → Effect RelaƟonships 1. Motion of Magnet • Towards coil: • S-pole → DeflecƟon leŌ, N-pole → DeflecƟon right • Away from coil: • S-pole → DeflecƟon right, N-pole → DeflecƟon leŌ 2. Speed of Movement • Slow push/pull → Small deflecƟon, Fast push/pull → Large deflecƟon • Shows: Induced current ∝ Rate of change of magnetic flux 3. Number of Turns • (10 turns → Small, 20 turns → Larger, 40 turns → Largest) deflecƟon • Shows: Induced current ∝ Number of turns 7 Key Conclusions 1.Magnitude of induced current depends on: – Rate of change of magnetic flux – Number of coil turns 2.Direction of in